The Global Nuclear Energy Partnership (GNEP) program requires spent fuel recycling and re-fabrication technologies with very low losses of actinide materials, low generation of secondary wastes, and remote operability. Traditionally, metal alloy nuclear fuel was cast using counter-gravity pressure-assisted injection. This technology culminated from parallel exploration of a number of fabrication approaches during the 1960s to the 1980s.
Typical operation involved heating the components of a metal alloy using induction coils around a yttria-coated graphite crucible for about 30 to 120 minutes. A vessel surrounding the furnace was evacuated and open bottom tips of tubes formed in about 175 quartz molds were lowered into the melt. The furnace vessel was pressurized by a rapid pulse and the molten fuel alloy was injected vertically upward into the tubes of the quartz molds. The molten fuel alloy rapidly solidified in the molds and the molds were withdrawn from the melt. The quartz molds were removed from the furnace and shattered to release fuel slugs for further fabrication into fuel pins.
The described technology became well-established and recognized as highly reliable and adaptable to remote operation. The process was used for remote fabrication of about 30,000 irradiated metal fuel pins and many more unirradiated (cold) pins of fuel alloys. In the 1990s, Japan adopted the same technology approach and continues its utilization for fabrication of metal fuel to support metal fuel research and development efforts.
Unfortunately, the described technology produces a significant high-level radiation waste stream from the shattered molds. Also, the crucible technology dates back to the 1940s and involves manual recoating and cleaning, which leads to metal fuel material losses in the removed coating dross. The recoating and cleaning is labor intensive and its effectiveness is operator dependent. Further, about 30% of the melt remains in the crucible as a heel that is recycled. Such extensive recycling limits process efficiency and generates a source of impurity buildup.
While the invention was motivated in addressing the above-identified issues, it is not so limited. The invention is only limited by the accompanying claims as literally worded, without interpretative or other limiting reference to the specification, and in accordance with the doctrine of equivalents.